Currently, distributed green energy resources represented by wind power, photovoltaic and other new energy power generation modes are developing rapidly. Especially, with construction of power market, traditional power users, such as factory and mine enterprises and ordinary households, can sell electricity to the power grid and become small power producers when the power purchase price of the power grid is high, as long as they are equipped with distributed green energy resources. However, connection of such flexible distributed power sources to the power grid needs to be established on the basis of accurate real-time monitoring of the operating state of the power grid, to ensure impact on the distributed power sources themselves and the power grid when the distributed power sources are connected to the power grid.
Traditional power monitoring devices mainly include fixedly mounted electric meters, power analyzers, etc. mainly for monitoring users. There are also power monitoring systems for large users, etc. Such types of monitoring instruments have the following major shortcomings. First, monitoring is mostly unidirectional, so the instruments can not be effectively applied to a distributed generation system featured by dynamic conversion between power user/power producer roles. Second, such a device only performs monitoring of one node, without relevant data sharing and powerful data analysis, and thus the operating state level of a monitored point can only be simply analyzed. Overall evaluative analysis of the grid-connected system and the power supplied user can not be achieved.
To achieve the above objects, a monitoring system needs to meet the following conditions. First, coupling indices of the power system and distributed power interfaces are selected to effectively achieve two-way monitoring of power producer role conversion of distributed power sources. Second, the monitoring system must be full-distribution and centralized-type, to achieve local characteristic monitoring of the distributed power sources in a full-distribution manner, and achieve overall grid-connected characteristic analysis of the distributed power sources and the grid-connected power system by using global information in a centralized manner. In view of the above problems, the invention provides a flexibly connectable dispersed state monitoring device for distributed generation. The device is applied at a distributed power producer and is switched flexibly according to whether the distributed power source is connected to the grid. The device has a network communication function, providing data collection basis for centralized grid-connected analysis.